A guard llama is a llama used in farming to protect sheep, alpacas, goats, hens or other livestock from coyotes, dogs, foxes and other predators. In the past, a single gelded (castrated) male was recommended. In more recent years it has been discovered that single, unbred females make better and safer guardians. They also do not pose the risk of attempting copulation (hence smothering) or chasing the smaller livestock.
Guard llamas may defend against predators in many ways. Llamas are instinctively alert and aware of their surroundings, and may draw attention to an intruder by making a startling alarm call that sounds like a rusty hinge. They may walk or run toward an intruder, and chase, paw at, or kick it. Some llamas may herd the animals they are guarding into a tight group or lead them away from danger and to the spot where they may feel the safest. Others may stand apart from the group and watch the intruder. Although llamas have been known to kill predators (such as coyotes), they should not be considered attack animals. They are generally effective against single intruders only, not packs. In the US, guard llamas have been most common in ranches located in western regions, where larger predators, such as the coyote, have been more prevalent. Not every llama will guard, however, and it should not be assumed that because it is a llama it will guard. 
Research suggests the use of multiple guard llamas is not as effective as one. Multiple males tend to bond with one another, rather than with the livestock, and may ignore the flock. A gelded male of two years of age bonds closely with its new charges and is instinctively very effective in preventing predation. Some llamas appear to bond more quickly to sheep or goats if they are introduced just prior to lambing. Many sheep and goat producers indicate a special bond quickly develops between lambs and their guard llama and the llama is particularly protective of the lambs.
Most research on the effectiveness of guard llamas has been done with sheep. A 1990 study by Iowa State University found that 80% of sheep producers with guard llamas rated them as effective or very effective. The study found average rates of loss to predators fell from 21% to 7% after the introduction of a guard llama. In other studies, over half of guard llamas completely eliminated losses due to predators. Dogs and coyotes have been injured and even killed by llamas.
- International Llama Association. (1995). "Guard Llamas." ILA Educational Brochure #2.
- Walker, Cameron. "Guard Llamas Keep Sheep Safe From Coyotes." National Geographic, June 10, 2003.
- Franklin, W. L. and Powell, K. J. (1994). "Guard Llamas: A part of integrated sheep protection." Iowa State University Extension Brochure.
- Andelt, W. J. (1995). "Livestock Guard Dogs, Llamas, Donkeys." Management. No. 1218
- California Department of Food and Agriculture. "Choosing a Guard Animal." Livestock Guardians. Brochure.